243 research outputs found
Awareness exposure and technology adoption: the case of orange-fleshed sweetpotato in West Africa.
Commonly used innovation adoption models indirectly assume homogenous information flow across farmers, which is often not the case. For new and or not well known technologies such as Orange-fleshed sweetpotato (OFSP) varieties, awareness exposure plays an important role in farmersâ decision to adopt. OFSP varieties have been shown to be highly effective means of combating it at the community level because of its high pro-vitamin A content and its cost effectiveness as compared with fortification and supplementation. Significant efforts, including the implementation of the Jumpstarting Orange-fleshed Sweetpotato project, have been deployed over the last decade in West Africa to promote the production and consumption of OFSP. Observations in the project countries indicating that the usage rate of OFSP among the beneficiaries was extremely high, suggesting a significant link between awareness activities and adoption behavior. Using the counterfactual outcome framework from the modern evaluation approach on 345 and 381 sweetpotato farmers from Ghana and Nigeria respectively, we found that the OFSP adoption rates could have been up to 61 percent in Ghana and 42 percent in Nigeria in 2016 instead of the observed sample adoption rate of 51 and 33 percent if the whole population was exposed to the OFSP varieties. This suggests that there is potential for increasing dissemination rate among population. Our study has showed that the OFSP adoption is influenced
by a number of factors, which vary between the study countries. This implies that actions to increase the adoption rate shouldnât be âone size fits all solutionâ approach
Multibarrier tunneling
We study the tunneling through an arbitrary number of finite rectangular
opaque barriers and generalize earlier results by showing that the total
tunneling phase time depends neither on the barrier thickness nor on the
inter-barrier separation. We also predict two novel peculiar features of the
system considered, namely the independence of the transit time (for non
resonant tunneling) and the resonant frequency on the number of barriers
crossed, which can be directly tested in photonic experiments. A thorough
analysis of the role played by inter-barrier multiple reflections and a
physical interpretation of the results obtained is reported, showing that
multibarrier tunneling is a highly non-local phenomenon.Comment: RevTex, 7 pages, 1 eps figur
Lorentz Invariant Superluminal Tunneling
It is shown that superluminal optical signalling is possible without
violating Lorentz invariance and causality via tunneling through photonic band
gaps in inhomogeneous dielectrics of a special kind.Comment: 10 pages revtex, no figure, more discussions added, submitted to
Phys. Rev.
On a universal photonic tunnelling time
We consider photonic tunnelling through evanescent regions and obtain general
analytic expressions for the transit (phase) time (in the opaque barrier
limit) in order to study the recently proposed ``universality'' property
according to which is given by the reciprocal of the photon frequency.
We consider different physical phenomena (corresponding to performed
experiments) and show that such a property is only an approximation. In
particular we find that the ``correction'' factor is a constant term for total
internal reflection and quarter-wave photonic bandgap, while it is
frequency-dependent in the case of undersized waveguide and distributed Bragg
reflector. The comparison of our predictions with the experimental results
shows quite a good agreement with observations and reveals the range of
applicability of the approximated ``universality'' property.Comment: RevTeX, 8 pages, 4 figures, 1 table; subsection added with a new
experiment analyzed, some other minor change
Multilocal fermionization
We present a simple isomorphism between the algebra of one real chiral Fermi
field and the algebra of n real chiral Fermi fields. This isomorphism preserves
the vacuum state. This is possible by a "change of localization", and gives
rise to new multilocal symmetries generated by the corresponding multilocal
current and stress-energy tensor. The result gives a common underlying
explanation of several remarkable recent results on the representation of the
free Bose field in terms of free Fermi fields, and on the modular theory of the
free Fermi algebra in disjoint intervals.Comment: 18 pages. v2: minor corrections, reference update
The resultant on compact Riemann surfaces
We introduce a notion of resultant of two meromorphic functions on a compact
Riemann surface and demonstrate its usefulness in several respects. For
example, we exhibit several integral formulas for the resultant, relate it to
potential theory and give explicit formulas for the algebraic dependence
between two meromorphic functions on a compact Riemann surface. As a particular
application, the exponential transform of a quadrature domain in the complex
plane is expressed in terms of the resultant of two meromorphic functions on
the Schottky double of the domain.Comment: 44 page
Neoadjuvant Systemic Therapy Use for Younger Patients with Breast Cancer Treated in Different Types of Cancer Centers Across the United States
Background Multiple clinical trials have shown that neoadjuvant systemic therapy has a benefit in women who are borderline lumpectomy candidates and in those with locally advanced breast cancers by reducing the mastectomy rate and making inoperable tumors operable. The study aim was to examine the patterns of neoadjuvant chemotherapy and endocrine therapy use among younger women in the United States treated at different types of cancer centers. Study Design Data from the National Cancer Data Base for 118,086 women younger than 65 years with clinical stage IIA (T2N0 only) to IIIC breast cancer. Following the National Comprehensive Cancer Network guideline categorization, patients were grouped into those who were borderline lumpectomy candidates (clinical stage IIA [T2N0 only], IIB, or IIIA [T3N1 only]) or those with locally advanced disease (clinical stage IIIA [T0-3N2 only], IIIB, or IIIC). The main outcome was the proportion of women who received neoadjuvant systemic therapy. Results Use of neoadjuvant chemotherapy ranged from 17% (stage IIA) to 79% (stage IIIB). Across almost all stage and receptor subtypes, the use was lower in community vs academic centers. On multivariable analysis, use of neoadjuvant chemotherapy was decreased in community vs academic centers (borderline lumpectomy candidates: adjusted risk ratio = 0.73; 95% CI, 0.69â0.77; locally advanced disease: adjusted risk ratio = 0.78; 95% CI, 0.74â0.83). Conclusions Use of guideline-concordant neoadjuvant chemotherapy is significantly higher among women treated at academic vs community centers in young and healthy women who do not commonly have contraindications to this treatment. Our study identified a potential disparity in cancer care by type of center where patients receive treatment
Evaluating the effectiveness of neoadjuvant chemotherapy in reducing mastectomy for women with breast cancer
Background: Neoadjuvant chemotherapy in breast cancer reduced mastectomy rates by 7% to 13% in randomized trials. However, the differential effects for women with different stages, receptor subtypes, and ages are unknown. We compared mastectomy rates in women who did vs did not receive neoadjuvant chemotherapy in 18 patient subgroups. The main objective was to quantify the potential benefit from neoadjuvant chemotherapy in reducing mastectomy rates for each subgroup. Methods: Our retrospective analysis used data from the National Cancer Data Base, which includes approximately 70% of incident cancers across the United States. Absolute risk reductions for mastectomy were determined for 18 subgroups of clinical stage, receptor subtype, and age group. In each subgroup, propensity score weighting balanced measured covariates between women treated with vs without neoadjuvant chemotherapy. Results: A total of 55 709 patients were analyzed. In clinical stage IIA disease, only patients with human epidermal growth factor receptor 2 (HER2)-positive tumors had reduced mastectomy rates associated with neoadjuvant chemotherapy (age < 60 years, 12%; age â„ 60 years, 12.6%). For stage IIB cancers, neoadjuvant chemotherapy was associated with an absolute reduction in mastectomy rates of 5.9% in women younger than age 60 years with hormone receptor-positive/HER2- disease, 8.2% to 10.7% for triple-negative disease, and 11.7% to 17.4% for HER2+ disease. For stage IIIA, the reductions in mastectomy rates ranged from 6.6% to 15.9%. Conclusions: In an analysis of patients treated across the United States, we found that neoadjuvant chemotherapy was associated with a reduction in mastectomy rates to a similar magnitude overall as shown in randomized trials, but this benefit varied widely by patient subgroup. This study provides novel information to help women make informed decisions regarding treatment
Thin-Film Metamaterials called Sculptured Thin Films
Morphology and performance are conjointed attributes of metamaterials, of
which sculptured thin films (STFs) are examples. STFs are assemblies of
nanowires that can be fabricated from many different materials, typically via
physical vapor deposition onto rotating substrates. The curvilinear--nanowire
morphology of STFs is determined by the substrate motions during fabrication.
The optical properties, especially, can be tailored by varying the morphology
of STFs. In many cases prototype devices have been fabricated for various
optical, thermal, chemical, and biological applications.Comment: to be published in Proc. ICTP School on Metamaterials (Augsut 2009,
Sibiu, Romania
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